1. Field of the Invention
The present invention relates to a backlight unit and a liquid crystal display (LCD) device and more particularly to an edge type backlight unit being capable of performing a local dimming driving and scan driving and an LCD device including the same.
2. Discussion of the Related Art
LCD devices, which are widely used for TV, monitors, TV, and so on because of their high contrast ratio and other characteristics that are suitable to display moving images, display images using an optical anisotropy and polarization properties of liquid crystal molecules.
The LCD device includes a liquid crystal panel. The liquid crystal panel includes a first substrate where a gate line, a data line, a thin film transistor and a pixel electrode are formed, a second substrate where a color filter layer and a common electrode are formed, and a liquid crystal layer which includes the liquid crystal molecules interposed therebetween. The alignment direction of the liquid crystal molecules is changed by an electric field in the liquid crystal panel such that light transmissivity is also controlled.
Generally since the liquid crystal panel does not include a light source therein, an additional light source is required. For example, a backlight unit including a light source is disposed under the liquid crystal panel to provide light onto the liquid crystal panel. The LCD device can display images using the light from the backlight unit.
A fluorescent lamp such as a cold cathode fluorescent lamp (CCFL) and an external electrode fluorescent lamp (EEFL) has been widely used as the light source of the backlight unit. Recently, a light emitting diode (LED) having advantages in power consumption, weight and brightness is developed and used as the light source of the backlight unit.
Generally, the backlight unit is classified into an edge light type and a direct type depending on a position of the light source. In the direct type backlight unit, the light source is positioned throughout directly under the liquid crystal panel such that the light from the light source is directly provided to the liquid crystal panel. In the edge type backlight unit, a light guide plate is disposed under the liquid crystal panel, and the light source is positioned at a side of the light guide plate. The light from the light source in the edge type backlight unit is refracted by the light guide plate to proceed to the liquid crystal panel.
In the direct type backlight unit, a local dimming where different voltages can be applied to each LED such that each LED emits light having a difference in brightness, or a scan driving where different voltages can be applied to each LED string, can be performed. However, more LEDs are required and thus power consumption is increased for the direct type backlight unit than the edge type backlight unit.
The edge type backlight unit has advantages in a production process, weight, a thin profile and power consumption. However, the edge type backlight unit has limitations in a scan driving and a local dimming driving in comparison with the direct type backlight unit.
In view of these limitations associated with the related art, an LCD device having a backlight unit that can provide advantages in weight, a thin profile, power consumption, image quality, etc. is desired.